Annotation of /trunk/SConstruct

A few changes in the build mechanism and the file structure so scons can build release tar files:
* paso/src/Solver has been moved to paso/src
* all test_.py are now run_.py files and are assumed to be passing python tests. they can run by
scons py_tests and are part of the release test set
* escript/py_src/test_ are moved to escript/test/python and are installed in to the build directory
(rather then the PYTHONPATH).
* all py files in test/python which don't start with run_ or test_ are now 'local_py_tests'. they are installed i
by not run automatically.
* CppUnitTest is now treated as a escript module (against previous decisions).
* scons realse builds nor tar/zip files with relvant source code (src and tests in seperate files)
the python tests don't pass yet due to path problems.